[macro-hold-caller]
exten => 4000,1,Set(HOLD=${ARG1})
exten => 4000,2,GotoIf($[ ${HOLD} = 1 ]?hold:unhold)
exten => 4000,n(hold)While(HOLD=1)
exten => 4000,n(unhold),Dial(${ARG2})

exten => 4001,1,Macro(hold-caller|1|${SOURCE_CHANNEL})
exten => 4002,1,Macro(hold-caller|0|${SOURCE_CHANNEL})